Abstract: To detect the relationship between horizontal distribution of fish assembles and water masses or between seasonal distribution of fish assembles and water masses, three fish trawl surveys were conducted in the southwest waters of the Nanri Islands in December 2009 and in April and August 2010. Density and distribution pattern of fish assemblages, body length, body weight, juvenile ratio, dominant species, index of relative importance, and contribution to the total number of dominant species were analyzed in the study. The results showed that fish densities in terms of both weight and number were higher in summer (2599.60 kg·km^-2, 22.6×10³ ind·km^-2) than those in spring (601.26 kg·km^-2, 17.3×10³ ind·km^-2) and winter (730.36 kg·km^-2, 22.6×10³ ind·km^-2). The average body length of fish was the highest in spring (14.95 cm), while the average body weight was the highest in winter (49.76 g). The proportion of juvenile was the highest in summer (as high as 81.72%). The variation in distribution pattern and biological parameters of fish assembles was probably associated with spawning and forging activities of fish. For example, it was mainly composed of spawning adult assembles in spring, while foraging juveniles were predominant in summer. Distribution pattern of fish assemblages was related to the seasonal variation in water mass and food availability in the coast water of Fujian. Fish densities were higher on the offshore side of Zhejiang-Fujian coastal water and Taiwan Strait warm current water. While in summer fish was more abundant in the nearshore region where food was particularly abundant. The distribution pattern of fish assemblages was consistent with the distribution pattern of dominant fish species.

Key words: Taiwan strait warm current water, Zhejiang-Fujian coastal water, fish assemblage, dominant species, water mass, forage